1. Field of Invention
This invention pertains to a method and apparatus for optimizing a process for encoding content based on a previous process for encoding the same content.
2. Description of the Prior Art
In the past, content, such as movies, were recorded optically on film, and then distributed in analog formats. However, digital cinema has been developed as a result of advances in digital signal processing and projection to the point where movies and similar multimedia presentations are now available in digital format. To generate a digital cinema digitally, movies are either shot directly or post-produced on a digital medium in an uncompressed video format, or are shot on film and are then converted and recorded on a digital medium. Once generated, the digital can be distributed either via hard drives, flash drives, optical discs (such as DVDs), electronically using various digital transmission schemes, etc. In the present application, the term “digital movie” is used to refer to a motion picture or other multi-media presentation recorded or shot on a film, developed and the resulting film was scanned to convert the content into a digital format. Various digital cameras and post platforms are available that can be used to record or post a film in either 2K or 4K format.
Popular format presently in use in the industry include the 2K and the 4K formats. There are several variations for each format, as illustrated by the following list:
Screen Resolution (and aspectCommon designationratio2K2048 × 1536 16 mm2K Academy projection2048 × 11072K TI DLP2048 × 10804K4096 × 3072 35 mm; 1.33 aspect4K Academy projection4096 × 2214 35 mm 1.66/1.85aspect4K4096 × 6144 35 mm VistaVision4K Academy Full Frame4096 × 2988 35 mm 1.37 aspect
Some cameras and post tools are available that have even higher resolutions.
The uncompressed video is then compressed and encoded into either a format compatible with digital projectors, e.g., the JPEG 2000 format, or a format compatible with a digital media such as MPEG-2, AVC, VC-1, MVC, etc. The second formats usually use a variable bit rate scheme in which the bit rate for each scene is determined by the authoring software and/or operator on a scene-by-scene basis and recorded in a respective log. The determination of the bit rate is made based on the complexity of the respective scene, dependent for example, on the amount of movement of actors or objects, correlated or uncorrelated motion vectors, edges or planes of activity, or other material changes from one set of frames to another.
One problem with these schemes is that, recently, there is a need to stream a digital movie at a relatively low bit rate over standard distributed networks (e.g., the Internet). However, a digital movie prepared for some distribution scheme (e.g. DVD or BD) in either format is often too large in size and bandwidth requirements, and therefore is not suitable for streaming or other low-bandwidth and/or file size distribution. Therefore, subsequent digital encoding of the content is required, and an efficient scheme to optimize quality is needed.
Moreover, since an encoding process has already taken place, information from this previous process is available that would make the new process, simpler, more reliable and/or more efficient.